1. Field of the Invention
The present invention relates to a wheel-speed sensor and, more particularly, to a wheel-speed sensor that can be more readily serviced, for example, without removal of a wheel axle or oil seal, unlike known wheel-speed sensors, and is relatively less complicated and less expensive to manufacture.
2. Description of the Prior Art
Wheel-speed sensors are known in the art. Such wheel-speed sensors are known to be used in vehicle applications for providing signals representative of the wheel-speed of the individual wheels on the vehicle. These wheel-speed signals are known to be used in anti-lock brake systems.
Examples of such wheel-speed sensors are disclosed in U.S. Pat. Nos. 5,537,032; 5,191,284; 5,293,124; and 5,476,272. U.S. Pat. Nos. 5,537,032; 5,191,284; and 5,293,124 relate to wheel-speed sensors which are integrated with a wheel-bearing assembly. U.S. Pat. No. 5,476,272, on the other hand, relates to a wheel-speed sensor that is integrally formed with an axle oil seal.
Referring first to U.S. Pat. Nos. 5,537,032; 5,191,284; and 5,293,124, these patents, as mentioned above, all relate to wheel-speed sensors which are integrated with wheel-bearing assemblies. U.S. Pat. No. 5,537,032 relates to a “between-the-rows” wheel-speed sensor, while U.S. Pat. Nos. 5,191,284; and 5,293,124 are wheel-speed sensors which are not disposed “between-the-rows” of a wheel-bearing assembly. Referring first to U.S. Pat. No. 5,537,032, this patent, as mentioned above, relates to a “between-the-rows” wheel-speed sensor which includes a magnetic exciter ring formed with alternating magnetic poles disposed between rolling element rows of a wheel-bearing. The magnetic exciter ring is formed from a ferro-magnetic material and is configured with a plurality of radially spaced tooth pairs. Each tooth pair is formed from a pair of axially spaced teeth forming a concentric notch relative to a magnetic exciter ring for receiving a variable reluctance sensor. A pole piece, configured in the same shape as the annular notch formed by the radially spaced tooth pairs, provides contour coupling between the magnetic exciter ring and the variable reluctance sensor. In operation, as the ferro-magnetic exciter ring rotates, electrical voltage pulses are induced in the variable reluctance sensor. The frequency of the pulses is representative of the wheel-speed.
There are several problems with the wheel-speed sensor disclosed in the '032 patent. For example, the wheel-speed sensor disclosed in the '032 patent requires a rather complicated magnetic exciter ring structure. Moreover, the serviceable portion of the sensor is located on the back side of the wheel mounting flange, thus requiring removal of the axle and/or oil seal for servicing.
U.S. Pat. Nos. 5,191,284; and 5,293,124 also relate to wheel sensors and are also configured to be integrated with a wheel-bearing assembly. In particular, U.S. Pat. No. 5,191,284 discloses a wheel-speed sensor which includes a generally C-shaped support that is adapted to be rigidly attached to a rotating inner ring of a wheel-bearing assembly. The C-shaped support is used to carry a pair of radially spaced-apart, magnetized rings forming an annular notch therebetween. A sensor which includes an extending pole piece is disposed within the notch. Thus, as the inner rotating ring rotates, the magnetic sensor is exposed to different magnetic poles, thus generating a signal representative of the wheel-speed.
U.S. Pat. No. 5,293,124 also discloses a wheel-speed sensor integrally formed with a wheel bearing. The wheel-speed sensor disclosed in the '124 patent is similar to the embodiment disclosed in the '284 patent, except that it discloses a single magnetic exciter ring formed from alternating North and South magnetic poles. Unfortunately, the wheel-speed sensors disclosed in both U.S. Pat. Nos. 5,191,284; and 5,293,124 suffer from the same problems as the wheel-speed sensor disclosed in U.S. Pat. No. 5,537,032. In particular, servicing of the sensor disclosed in U.S. Pat. Nos. 5,191,284; and 5,293,124 requires removal of the wheel bearing—a relatively cumbersome and labor-intensive task. In addition, the configuration of the exciter rings disclosed in U.S. Pat. Nos. 5,191,284; and 5,293,124 is relatively complex, thus requiring relatively expensive manufacturing. Thus, there is a need for a wheel-speed sensor that is easily serviceable and is less complicated and thus less expensive to manufacture than known wheel-speed sensors.